Method of making sealed electric batteries



Oct 17, 1967 .1. M. STROBEL ETAL 3,347,710

METHOD OF MAKING SEALED ELECTRIC BATTERIES Filed July 1, 1965 J 20 Fig. 1 I w 2 19 T 16 I I 2e it 2 'if 22 Fig. 2

INVENTORS J OSEFM KOBEL BY @E/QVW/YRD #445 A 77a ems v; v

United States Patent ()fitice 3,347,710 Patented Oct. 17, 1967 U 2 Claims. (or. 136-175) ABSTRACT OF THE DISCLOSURE This invention is a method of sealing a battery to prevent gas and liquid leakage. The battery consists of two metal open-ended cans or cups, one larger than the other, chemical battery material and a plastic tubular seal. The

assembly takes place in a vacuum by filling one cup with the battery material, placing the plastic tube over the cylindrical wall of the smaller can, and forcing the larger can down over the tube.

The invention relates to an electric primary cell or a storage battery and a process for its production.

The construction according to the present invention finds its application mainly in very small primary cells or storage batteries. Such batteries are used in wrist watches and hearing aids. The proper sealing of such very small cells has been diflicult and intricate.

In accordance with the present invention, an outer larger metal cup, open at its top, has in its lower part a pill of chemically reactive material which is electrically connected with the bottom. A second smaller metal cup open at its bottom has within it a second chemically reactive pill. A plastic intermediate tube, for insulation and sealing, is positioned between the two metal containers. The tube is under radial pressure, preferably over its entire length.

The construction avoids a crimping process. The radial compressing of the tube between the two containers gives a simple and safe sealing of their contents.

According to the present invention, the outside diameter of the intermediate plastic tube is larger than the inside diameter of the larger metal cup in order to obtain radial pressure on the tube. In this construction it is suflicient to press fit the single parts together to obtain the radial pressure on the tube and sealing.

According to the method of the present invention, the assembly and easing of the pills, containers and tube occurs in a vacuum. This presents overpressure in the interior of the hermetically closed cell. The presence of empty spaces (an under pressure) has a favorable e-ifect because, when the outer sealing vacuum is ended, the tube and the cups are drawn into the interior.

A preferred embodiment of the present invention is shown in the attached drawing. Other characteristics and advantages of the present invention will be apparent from the drawing and description. In the drawing:

FIG. 1 is a partially cut-away side view of -a battery ce-ll according to the present invention with the tube and bottom cup shown in sectional View; and

FIG. 2 is a cross section taken through the intermediate plastic tube prior to its insertion between the containers.

As shown on FIG. 1, the bottom metal cup (can or container) 10 includes a cylindrical shell 11, a shell bottom 12, and a top shoulder 13 on its outer edge. A mesh metal disc 14 rests against the inside of the shell bottom 12. Disc 14 in free condition is convexly curved (dome shaped), however, in assembled condition it adopts a plane shape, as shown in FIG. 1. An inner chemically reactive pill 16 is positioned on top of the mesh metal disc 14. An upper chemically reactive pill 18 is positioned in metal cup (container) 20. Several separators 19 are provided between the pills 18 and 16.

An intermediate plastic tube 22 electrically insulates cup 20 from cup 10.

The wall thickness of the tube 22, according to the invention, is preferably smaller than 0.3 mm. An advantageous construction results from a wall thickness of the intermediate tube of 0.2 mm. The intermediate tube 22 has preferably a length of at least 44 mm. in order to obtain good sealing between the metal containers. A particularly favorable plastic for the intermediate tube 22 is poly-tetra fluoro-ethylene (PTFE) such as Du Ponts Teflon T.M. It has high elasticity and provides very good insulation and sealing.

The intermediate tube 22 rests with its shoulder 24 against the top shoulder 13 of the metal cup 10. Tube 22, in free condition (see FIG. 2), has a tapered outer rim 26 on its lower end and a tapered inner rim 28 on its upper end. Both these rims are no longer noticeable in FIG. 1 because the intermediate tube, after insertion between the containers is transformed and stretched. Seen in its entirety, the intermediate tube 22 after insertion is under stress in the longitudinal direction.

To assemble the cell, the parts are placed in a vacuum chamber with a vacuum of at least Torr. Then, the upper cup is pressed down into tube 22. The tube, with cup 20, is then pressed into cup 10. The intermediate tube is slightly stretched during the press fit of the inner can 18. The shell 11 of the metal cup 10 and the metal cup 20 exert radial pressure against the intermediate tube 22. This pressure causes the intermediate tube to be compressed and to remain under a continuous stress.

By this construction a relatively good sealing of the pills is obtained; the upper cup is sealed against the lower metal cup; and the entire content of the cell is sealed from the exterior.

The cell may either be a primary cell or a storage battery depending upon the chemical materials used in pills 16 and 20.

We claim:

1. The process of sealing a battery consisting of an outer metal cylindrical cup closed at one end, an inner metal cylindrical cup closed at one end, chemically reactive battery material, and a plastic tubular sealing and insulating member whose outer diameter is greater than the inner diameter of the outer can; the steps consisting of forming a vacuum around the parts to be assembled, placing the chemical material in the inner can, placing the tube over the inner can, and forcing the outer can over the tube by pressure on the said cans.

2. The process as in claim 1 wherein the vacuum is at least 100 Torr.

References Cited UNITED STATES PATENTS 2,571,616 10/1951 Ruben 136-107 X 2,636,063 4/1953 Schroeder 136-133 2,843,650 7/1958 Jacquier 136-133 X WINSTON A. DOUGLAS, Primary Examiner. D. L. WALTON, Assistant Examiner. 

1. THE PROCESS OF SEALING A BATTERY CONSISTING OF AN OUTER METAL CYLINDRICAL CUP CLOSED AT ONE END, AN INNER METAL CYLINDRICAL CUP CLOSED AT ONE END, CHEMICALLY REACTIVE BATTERY MATERIAL, AND A PLASTIC TUBULAR SEALING AND INSULATING MEMBER WHOSE OUTER DIAMETER IS GREATER THAN THE INNER DIAMETER OF THE OUTER CAN; THE STEPS CONSISTING OF FORMING A VACUUM AROUND THE PARTS TO BE ASSEMBLED, PLACING THE CHEMICAL MATERIAL IN THE INNER CAN, PLACING THE TUBE OVER THE INNER CAN, AND FORCING THE OUTER CAN OVER THE TUBE BY PRESSURE ON THE SAID CANS. 